This invention relates to a photosensitive member containing a specific hydrazone compound with a styryl structure.
In electrophotography, copied images are formed by various methods. For example, the surface of a photosensitive member is charged and irradiated to form electostatic latent images thereon, the electrostatic latent images are developed to visible images by a developer, and then the developed images are fixed directly onto the photosensitive member (this method is referred to as a direct method). Alternatively, developed electrostatic latent images on a photosensitive member which are made visible by a developer are transferred to a copying paper and then, the transferred images are fixed on the paper (this method is referred to as a powder transferring method). In another method, electrostatic latent images on a photosensitive member are tranferred onto a copying paper, the transferred electrostatic latent images are developed by a developer and then fixed on the copying paper(referred to as an electrostatic latent image transferring method).
Known photosensitive materials for forming a photosensitive member as above mentioned include inorganic photoconductive materials such as selenium, cadmium sulfide or zinc oxide.
These photosensitive materials have many advantages such as low loss of charges in the dark, an electrical charge which can be rapidly dissipated with irradiation of light and the like. However, they have disadvantages. For example, a photosensitive member based on selenium is difficult to produce, has high production costs and is difficult to handle due to inadequate resistivity to heat or mechanical impact. A photosensitive member based on cadmium sulfide or zinc oxide has defects such as its unstable sensitivity in a highly humid environment and loss of stability with time because of the deterioration of dyestuffs, added as a sensitizer, by corona charge and fading with exposure.
Many kinds of organic photoconductive polymers such as polyvinylcarbazole and so on have been proposed. These organic photoconductive polymers have superior film forming properties, are light in weight, etc., but inferior in sensitivity, durability and environmental stability compared to the aforementioned inorganic photoconductive materials.
Physical properties or electrophotographic properties of a coating layer as a photosensitive member may be adjusted desirably by using an organic photoconductive material of low molecular weight in the combination with a selected binder resin, a selected composition or the like. However, the high mutual solubility of an organic photoconductive material with a binder resin is required because the photoconductive material is used together with the binder resin.
A photosensitive member prepared by dispersing an organic photoconductive compound of low molecular weight or high molecular weight in a binder resin has problems such as high residual potential caused by many traps of carriers, low sensitivity and the like. Therefore, a charge transporting material is further incorporated in a photosensitive member in order to overcome the problems as above mentioned, and a function-divided photosensitive member of a laminated or a dispersed type has been also proposed, in which charge generating function and charge transporting function are divided by different layers or different dispersed materials.
Many kinds of organic compounds are used as a charge transporting material, which have, however, many problems. For example, 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole disclosed in U.S. Pat. No.3,189,447 is low in compatibility with a binder and liable to separate out. A diarylalkane derivative disclosed in U.S. Pat. No.3,820,989 is good in mutual solubility with a binder resin, but changes in sensitivity when used repeatedly. A hydrazone compound disclosed in JP Laid-open No. 54-59143 is relatively good in residual potential properties, but being poor in chageability and repetition properties.
In practice, there are few organic compounds suitable for the preparation of a photosensitive member as above mentioned.